Question

Clean water should have BOD value:
A. <5 ppm
B. >5 ppm
C. <10 ppm
D. <2 ppm

Answer 1

BOD is the short form of the biochemical oxygen demand which is actually the amount of oxygen that is dissolved and required by the aerobic bacteria. They need it in order to decompose the organic waste that is basically present in the water sample at a particular temperature and pressure in the atmosphere.

Complete step by step answer:
As we have already discussed about the definition of BOD. Let us know about the BOD value of clean water.
The water that is used for the purpose of drinking should have a BOD level of around 1-2 ppm. This is considered healthy for the purpose of intake and normalcy. When the level of BOD changes to the range of 3-5 ppm, it is considered to be moderately clean.
The water that is polluted has a BOD of around 6-9 ppm. It is found that some amount of organic waste is present in the polluted water. This organic amount is decomposed by bacteria. This is the reason for high BOD. If the BOD level of water is high to the level of 100 ppm then the water sample should be considered highly polluted and can cause problems if consumed.
Clean water should have a BOD value of less than 5 ppm.

So, the correct answer is Option A.

Note: When the BOD value of the sample of water taken is high, the level of dissolved oxygen is less and the organism that needs a high amount of dissolved oxygen cannot survive in those conditions.
Ppm stands for parts per million.